In cellular communication systems, communication channels are generally assigned to a subscriber unit when an acquisition request is received by the system. The assigned communication channel is chosen so as not to interfere with other communication channels currently in use in the same cell or region that the subscriber unit is located. The assigned communication channel is also chosen so as not to interfere with other communication channels currently in use in neighboring cells.
Prior art communication systems that allocate communication channels based on predicted traffic demand suffer from the problem that predicted demand is not very accurate. This results in improper allocation of channels and is inefficient. Real-time channel allocation optimally requires complete knowledge of all channel assignments within the system. Because of propagation delays and limited data-link capacities, real-time knowledge of channel assignments is impractical in a global communication system.
In a global communication system that includes satellite communication stations, an optimum approach to channel allocation and assignment requires global knowledge of all channels assigned and presently in use. An advantage to global knowledge is that indirect interaction between channel assignments on satellites can be planned which allows for maximum utilization of available channel resources. For example, channels assigned over India have an impact on the channels available to be assigned over Europe by restricting the channels that may be assigned in Central-Asia and the Middle-East. Real-time knowledge allows the placement of capacity where the demand is. Disadvantages to this approach include the limited ability to transfer this information in real-time when the communication covers great distances. Other disadvantages to global knowledge approaches include the extensive use of data channels to continually transfer channel assignment information.
Thus what is needed are a method and apparatus to dynamically assign communication channels to subscriber units in real-time without complete knowledge of all channel assignments in the system. What is also needed are a method and apparatus for assigning communication channels that have the effect of real-time knowledge without the disadvantages discussed above. Further, what is needed are a method and apparatus that assigns communication channels to subscriber units using a channel reuse scheme that avoids interference with other assigned channels in a satellite-based communication systems.